Quiver scale in legend pointing north

I have quiverscale.m code downloaded I have U and V matrix (1*30) vectors each 30 corresponds to height bin.

my code : quiver(U,V,'autoscale','off'); quiverscale(max(max(U)),max(max(V)),gca);

This is not what I wish for I wish to have a legend which is an arrow of fixed length pointing North with its representative value written beside it

and all arrows in the plot to be scaled according to this legend within the plot!

Any help shall be highly appreciated!

Thanks in advance!